Evaluation of CO and SF6 as quantitative tracers for fossil fuel

CO2:

The Experimentalists’ view

Ingeborg Levin1, Ute Karstens2, Ulrike Gamnitzer1,Christoph Schönherr1, Bernd Kromer1

and Samuel Hammer1

1Institut für Umweltphysik Universität Heidelberg

2Max-Planck-Institut für Biogeochemie, Jena

February CO2 Fluxes

Fossil fuel CO2

(EDGAR V3.2 FT, Olivier et al., 2005)

Biome-BGC NEE (Churkina et al., 2003)

10-9 kg C m-2 s-10 10 20 30 40 50-10

Heidelberg: February 2002 (REgional MOdel)

Heidelberg: June 2002 (REgional MOdel)

Schauinsland: February 2002 (REgional MOdel)

Can we validate these model results ?

… measure total CO2 and

fossil fuel CO2

—› measure Radiocarbon (14C) in atmospheric CO2 …

… because fossil fuel CO2 contains no 14C and dilutes

atmospheric 14CO2

Long-term 14CO2 background observations in Europe

„clean“ 14CO2

background level in the Alps

Reference: Atmosphere in 1890

0

200

400

600

800

1000

1950 1960 1970 1980 1990 2000

14CO2 Vermunt

14CO2 Jungfraujoch

14C tree rings [Stuiver and Quay, 1981]

14C

[‰]

1985 1990 1995 2000 20050

50

100

150

200

continental reference Schauinsland monthly means Heidelberg monthly means

14

C [‰

]

Long-term 14CO2 observations in Europe

„clean“ 14CO2

background level in the Alps

Depletion of the 14CO2 level close to fossil fuel sources

Monthly mean fossil fuel CO2 at Schauinsland station and in

Heidelberg

mean fossil fuel CO2 offset:

Schauinsland:ca. 1.4 ppm

Heidelberg:ca. 10 ppm

0

50

100

150

200

continental reference Schauinsland monthly means Heidelberg monthly means

1

4C

[‰]

0

5

10Schauinsland

1985 1990 1995 2000 20050

20

40 total offset fossil fuel offset

Heidelberg

foss

il fu

el C

O2 [p

pm

]

… but the temporal resolution of our 14C measurements is poor:

weekly means

… and the sensitivity is quite low:

minimum uncertainty

≈ ±2.5 ‰ of 370 ppm ≥ ±1 ppm

—›proxies/surrogates needed

to substitute 14CO2 observations

Carbon Monoxide (CO)

Sulfur Hexafluoride (SF6)

29.09.2004 01.10.2004 03.10.20040

15

30

SF

6 [p

pt] 1.4 ppm

0

300

600

CO

[ppb

]

350

400

450

29.09.2004 01.10.2004 03.10.2004

CO

2 [p

pm]

Continuous trace gas observations in Heidelberg in October 2004

CO2

CO

SF6

CO: Mainly anthropogenic sources (fossil fuel burning) and oxidation of hydrocarbons

chemical life time ca. 2 months

SF6: Only anthropogenic sources roughly distributed according to population density

chemically inert

14CO2, fossil fuel CO2 and CO offset in Heidelberg

2001 2002 2003 20040

20406080

100120

2001 2002 2003 20040

200

400

Jungfraujoch (background)

14C

[‰]

Heidelberg

2001 2002 2003 20040

10

20

30fossil fuel CO

2

CO

2 [ppm

]

C

O [p

pb]

CO offset

How well can we quantitatively

use CO

as a fossil fuel CO2 surrogate ?

Weighted mean ratio [ppb/ppm]:

Observations: 12.2±0.4

Fossil fuel CO2 and CO offset and their ratio

2001 2002 2003 20040

200

400

2001 2002 2003 20040

10

20

30

2001 2002 2003 20040

10

20

30fossil fuel CO

2

CO

2 [pp

m]

C

O [p

pb

]

CO offset

ratio

[pp

b/p

pm

]

CO/CO2foss

Weighted mean ratios [ppb/ppm]:

Observations: 12.2±0.4

Emissions Inventories (incl. soils, etc.)

Edgar: 14.7

Fossil fuel CO2 and CO offset and their ratio in comparison with emissions

inventories

2001 2002 2003 20040

200

400

2001 2002 2003 20040

10

20

30

2001 2002 2003 20040

10

20

30fossil fuel CO

2

CO

2 [pp

m]

C

O [p

pb

]

CO offset

EDGAR

ratio

[pp

b/p

pm

]

CO/CO2foss

Weighted mean ratios [ppb/ppm]:

Observations: 12.2±0.4

Emissions Inventories (incl. soils, etc.)

IER: 18.0Edgar: 14.7

Fossil fuel CO2 and CO offset and their ratio in comparison with emissions

inventories

2001 2002 2003 20040

200

400

2001 2002 2003 20040

10

20

30

2001 2002 2003 20040

10

20

30fossil fuel CO

2

CO

2 [pp

m]

C

O [p

pb

]

CO offset

IER EDGAR

ratio

[pp

b/p

pm

]

CO/CO2foss

IER: Institute of Energy Economics and Rational Use of Energy, Stuttgart

Conclusions (I):

• Fossil fuel CO2 (FFCO2) emissions in Europe contribute almost half to the continental CO2 signal

• Monthly mean fossil fuel CO2 levels at urban sites can be determined by high precision 14CO2 measurements to better than ±10% in winter and about ±30% in summer.

• At remote sites, the mean FFCO2 signal is small (1-5 ppm) and can be determined by 14CO2 measurements only to about 30%. Higher temporal resolution of 14CO2 measurements is required here to achieve better precision.

Conclusions (II):

CO is a potentially applicable surrogate tracer for FFCO2,

however,

• Emissions inventories of CO (and FFCO2) are yet not accurate enough to apply it quantitatively,

• CO has sources other than from fossil fuel burning (soils !!) which also need to be known accurately

• The catchment area and relative mix of emissions needs to be known accurately, this requires modelling

See REMO results from Karstens et al., Poster FF-134

Thank you !

Comparison of measured and REMO-modelled CO and FFCO2 mixing

ratios

Comparison of measured and REMO-modelled CO/FFCO2 ratios

See also Poster by Ute Karstens et al. No. FF-134

Mean ratios [ppb/ppm]:

Observations: 13.5±0.6

REMO & EDGAR: 12.7±0.1

REMO & IER: 11.0±0.2

CO/CO2 fossil fuel emission ratios 2000

IER mean 2000(Scholz et al., IER 2005)

EDGAR V3.2 FT 2000 (Olivier et al., 2005)

in mmol / mol